1. Field of the Invention
The invention relates to open thread screw and cap mechanisms with particular application to forming collapsible tube dispensers.
2. Background Information
This application is a continuation in part of two applications previously filed for the applicants disclosing reusable, collapsible tube dispensers. While the earliest collapsible tube dispensers in the US patent database date from the early nineteenth century, there were problems reported with the prior art which the previous applications addressed, namely:                The prior art collapsible tubes do not lend themselves both to being reusable and supporting the complete, controlled dispensing of their contents. As the term is used herein, reusable will refer to the capability to dispense small, or controlled, portions of the contents multiple times, perhaps on different occasions. Reusable may further refer to the capability to refill the contents multiple times. And reusable may further refer to a container, which can be cleaned, and refilled with differing contents.        With the exception of some one-time use containers, prior art collapsible tube dispensers typically possess a rigid shoulder and a rigid throat. The rigid throat provides an exterior, rigid screw. This exterior rigid screw mates with a cap providing a matching interior screw pattern. When the cap is screwed onto the exterior screw of the throat, a seal is formed, which seals in the contents of the collapsible tube.        
There are several terms which will be used herein:                Personal care products include, but are not limited to, cosmetics, facial care products, skin care products, over-the-counter health products, and/or hair care products.        Open thread screws have threads that taper away from the body, or remain of constant thickness. Up until the parent applications, using these open thread screws required that the throat and the threads of a collapsible tube be essentially rigid. An essentially rigid throat on a collapsible tube dispenser virtually guarantees that some of the tube contents will not readily leave the tube, causing the tube to waste some of its contents. The rigid shoulder further guarantees this waste.        
FIG. 1A shows a prior art exterior screw 20 with a prior art external flexible thread form 22. The prior art external flexible thread form 22 is shown in an expanded view through the following examples shown in FIGS. 1B and C with a matching internal thread form 24.
There is a local coordinate system in FIG. 1A, which will be used throughout this document. The z axis 10 extends through the center of the cylinder of the prior art exterior screw 20, and is the central axis of the cylinder. The r axis 12 is the radial direction of the thread at a point, which, for the sake of discussion, is referred to as thread point 22 in FIG. 1A. The n axis 14 is normal to the thread point 22. When the screw is turned in the n direction, it engages more of the threads.
The engagement of an exterior screw thread and matching interior screw is shown in the expanded view of the prior art open screw thread 22 in FIG. 1A. The expanded view is a cross-section of the threads taken in the plane of the z axis 10 and the r axis 12.
FIG. 1B shows an example of FIG. 1A using a standard acme thread for the external flexible thread form 22 and the matching internal thread form 24. A first external acme thread 22-1 matches the first internal acme thread 24-1. A second external acme thread 22-2 with the second internal acme thread 24-2.
FIG. 1C shows an example of FIG. 1A using a standard buttress thread for the external flexible thread form 22 and the matching internal thread form 24. A first external buttress thread 22-3 matches the first internal buttress thread 24-3. A second external buttress thread 22-4 with the second internal buttress thread 24-4.
FIG. 1D shows an example of FIG. 1A using a box thread for the external flexible thread form 22 and the matching internal thread form 24. A first external box thread 22-5 matches the first internal box thread 24-5. A second external box thread 22-6 with the second internal box thread 24-6. One skilled in the art will recognize that FIGS. 1B to 1D show some of the many variations in open threads in use today. Other commonly used threads include various “V” shaped threads, as well as variations in angles of the walls, variations in the shape of the peaks and troughs of the threads.
To summarize from the parent applications, what is needed and has been addressed in them are reusable collapsible tubes able to dispense essentially all of its contents.